1. Field of the Invention
The present invention relates to a manual winch with a safe release mechanism, more particularly, the present invention relates to a manual winch with dual locking dogs and a method of retrofitting existing winches.
2. Prior Art
Winches are commonly used for winding and reeling cable and rope for lifting, pulling, towing, guiding and the like of any number of objects. A wide variety of powered and manual winches have been developed. Manual winches remain in common use where a powered winch would be impractical or inefficient. Even in a manual winch the operator, through various mechanical advantages, can generate a very large tension on the cable. Such high load manual winches are common in marine environments for towing barges and the like. Examples of manual winches are described in greater detail in U.S. Patent No. 5,947,450 which is incorporated herein by reference.
In a high load manual winch there is some concern to the operator in releasing the load and unwinding the reel, also called a drum. The high load manual winch will have some type of locking mechanism to hold the load and prevent the drum from unwinding. One typical locking mechanism is a pawl, also called a locking dog, which is engaged with a gear to prevent the gear and the associated drum from unwinding. Consequently, an engaged locking dog is essentially receiving the load of the cable through the drum and the associated gear. In one conventional design, a loading or actuating lever is coupled to the gear through further gearing for winding and unwinding, also called loading and unloading, of the drum and the locking dog. It is common for an operator to use an extension to the loading lever to increase the mechanical advantage provided. In the unwinding operation, the loading lever is moved, possibly with an extension, until the load on the locking dog is released. At this point, the locking dog can be moved into a disengaged position and the winch is able to be unwound or paid out. A handwheel, with a foot brake if needed, can be used for unwinding the drum. The concern in this pay out operation is that at the point that the locking dog is disengaged the entire load will be carried by the operator through the loading lever and the extension. Under high loads this may be difficult to control for the operator as he moves to the handwheel.
It is an object of the present invention to minimize the drawbacks of the existing manual winches and to provide a simple easier method of unwinding. A further object of the present invention is to provide a system which can be retrofitted onto existing manual winches.
In the development of the present invention satisfying the above objects, the Applicants have created a manual winch with dual locking dogs described hereinafter. Winches with two locking dogs operating on a ratchet wheel have been known in the prior art. One common version is to form a double-tipped brake pawl such that one end or the other end of the brake pawl, i.e., either of the two locking dogs is alternately engaged with the ratchet wheel. A ratchet wheel using this double dog technology is sold under the PNW-1000 manual ratchet. Another winch incorporating this design is the HD-100 and HD-300 of Fugi Seiko winch products. A separate two dog winch mechanism is to have dogs operating in opposite directions such that one of the dogs can be operated depending on in which direction the drum is being wound. Such a reverse dog assembly can be found in the Wintech spur gear series. A third type of winch utilizing two locking dogs is a W-100 barge connector winch manufactured by Blackburn. In this device, the two pawls are connected together by a linkage mechanism so that they alternatively engage the single gear. To some extent, in operation this is similar to the double-tipped brake pawl which pivots to selectively have one dog engage the wheel. The deficiency in all of the prior art dual dogs is that there is no independent operation of the dogs. In the double-tipped device and the Blackburn device, the dogs are connected such that only one of the dogs can be operated In the reverse dog configuration of Wintech, only one of the locking dogs can hold the load depending on the direction in which it is turning. This prior art does not solve the problems addressed with the present invention. There still remains a need in the industry for dual locking dogs where each locking dog is operated independently such that, selectively, either one, neither, or both can be biased towards and engaged position.
The objects of the present invention are achieved by a manual winch with dual locking dogs according to the present invention. The present invention is designed to be easily retrofitted into existing winches. The design of the present invention includes a housing supporting a rotatable drum upon which the cable is reeved. A pair of gears are attached to the drum with a locking dog that may be engaged with each gear, wherein the drum is prevented from unwinding with at least one locking dog engaged with a respective gear.
These and other advantages of the present invention will be clarified in the description of the preferred embodiments wherein like reference numerals represent like elements throughout.